Manual dressing apparatus

ABSTRACT

In a dressing apparatus for manually dressing a grinding wheel, a dressing housing is slidably mounted on a supporting bracket being pivoted thereto by a pivot pin for permitting sliding movement only in a horizontal plane. A shaft carrying a dressing tool is slidably but non-rotatably received in the dressing housing for adjusting the axial position of the dressing tool. A positioning member having a reference edge which is spaced apart from the pivot pin by a predetermined distance is carried by the dressing housing and means are provided for indicating the position of the dressing tool relative to the reference edge. In addition, the dressing housing is adapted to selectively be rotated freely and within predetermined limits on the supporting bracket and to be locked against rotation relative thereto.

Kobayashi et al.

[ Apr. 2, 1974 MANUAL DRESSING APPARATUS [75] Inventors: Akiyoshi Kobayashi, Kariya; Kiyoshi Miyagawa, Anjo, both of Japan [73] Assignee: Toyoda Koki Kabushiki Kaisha,

Kariya-shi, Aichi-Ken, Japan 22 Filed: Dec.22, 1971 211 Appl. No.: 210,781

[30] Foreign Application Priority Data 7 I Dec. 24, 1970 Japan 45-131416 [52] US. Cl. 125/11 AT [51] Int. Cl B241) 53/04 [58] Field of Search 125/11 A, 11 AT, 11 AS [56] References Cited UNITED STATES PATENTS 7 2,708,433 5/1955 Andre. 125/11 A 2,642,856 6/1953 Calloway 125/11 AT 2,446,833 8/1948 Johnson 125/1 1 AT 3,474,772 10/1969 Sirois 125/11 R 3,498,161 3/1970 Kump 125/11 AT 2,815,017 12/1957 Bordonaro 125/11 AT Primary Examiner-Harold D. Whitehead Attorney, Agent, or Firm0blo'n, Fisher, Spivak, Mc- Clelland & Maier [57] 7 ABSTRACT In a dressing apparatus for manually dressing a grinding wheel, a dressing housing is slidably mounted on a supporting bracket being pivoted thereto by a pivot pin for permitting sliding movement only in a horizontal plane. A shaft carrying a dressing tool is slidably but non-rotatably received in the dressing housing for adjusting the axial position of the dressing tool. A positioning member having a reference edge which is spaced apart from the pivot pin by a predetermined distance is carried by the dressing housing and means are provided for indicating the position of the dressing tool relative to the reference edge. in addition, the dressing housing is adapted to selectively be rotated freely and within predetermined limits on the supporting bracket and to be locked against rotation relative v thereto.

11 Claims, 10 Drawing Figures PATENTED 2 L974 SHEET 1 BF 4 INVENTORS AKIYOSHI KobAyAsm Kwosm MIYAGAWA BY a Wfiiffm ATTORNEYS PATENIEDAPR 2 SHEEI 2 0F 4 PATENTED APR 2 I974 saw 3hr 4 MANUAL DRESSING APPARATUS BACKGROUND OF THE INVENTION 1. Field Of The Invention This invention relates generally to grinding machines and more particularly to a dressing apparatus for manually dressing a grinding wheel wherein a dressing housing having a dressing tool is rotatable relative to a supporting bracket in a horizontal plane and within predetermined limits for dressing various contoured peripheral portions of a grinding wheel.

2. Description Of The Prior Art In conventional dressing apparatus for manually dressing a grinding wheel to a predetermined shape, an exclusive gauge hheretofore has been provided for eating a dressing tool in a position corresponding to the radius of a peripheral portion of a grinding wheel to be dressed. although this method has been somewhat successful for its purpose, it has not been altogether satisfactory, however, since the exclusive gauge must be exchanged for another gauge each time the radius of the peripheral portion of the grinding wheel is changed, and this requires a laborious operation which takes a great deal of time to perform.

Moreover, in the conventional dressing apparatus, a

I dressing housing is selectively permitted to rotate freely and within limits and to be locked against rotation relative to a supporting bracket by means of a plurality of 1 individual devices, which also involves a laborious operation which takes a long period of time to effect.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved manual dressing apparatus which is simple in construction and is easier to operate than apparatus of the same character heretofore available.

Another object of the present invention is to provide an improved manual dressing apparatus including a positioning member having a reference edge for exactly positioning a dressing tool according to a radius of a peripheral portion of a grinding wheel.

A further object of the present invention is to provide an improved manual dressing apparatus including a single means for selectively permitting a dressing housing to be rotated freely and within predetermined limits and to be locked against rotation relative t'o'a supporting bracket for the purpose of performing a dressing operation.

The foregoing and other objects are attained according to the present invention by a dressing apparatus for manually dressing a grinding wheel which comprises a table slidable in a path parallel to the axis of the grinding wheel, a supportingbracket mounted on the table and a dressing housing slidably mounted on the supporting bracket and being pivotally connected thereto by a pivot pin for permitting sliding movement about the pivot pin in an arcuate path and only in a horizontal plane. A shaft is slidably but non-rotatably received in the dressing housing such that its axis passes through the axis of the pivot pin and a dressing tool is secured to the shaft for dressing the grinding wheel. Means are provided for adjusting the axial position of the dressing tool and a positioning member having a reference edge edge being spaced apart from the axis'of the pivot pin by a predetermined distance. Indicating means are provided for indicating the relative position of the dressing tool to the reference edge. A manual hand lever is secured to the dressing housing for rotating the dressing housing in the horizontal plane, and selective means are provided on the supporting bracket for selectively permitting the dressing housing to be rotated freely by the hand lever within preselected limits and to be locked against rotation relative to the supporting bracket.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of a preferred embodiment of the present invention when considered in con? nection with the accompanying drawings, in which like reference numerals designate like or corresponding parts 7 throughout the several views thereof, and wherein:

FIG. 1 is a plan view of a dressing apparatus embodying the present invention;

FIG. 2 is a sectional view taken along the line IIII of FIG. 1, illustrating the dressing housing being pivotably mounted on the supporting bracket and carrying the dressing tool and its axial adjusting means, and the selective device for preselecting the limits of rotation of the dressing housing;

FIG. 3 is a partial front view of the apparatus shown in FIG. 1, illustrating the dressing tool positioning member;

FIG. 4 is a sectional view taken along the line IV-IV of FIG. 2, illustrating various positions of selection of rotational limits for the dressing housing;

FIG. 5 is a sectional view taken along the line V V of FIG. 2 showing one operational position of the selecis connected to the dressing housing, with the reference tive device wherein the dressing housing is precluded from moving relative to the supporting bracket;

FIG. 6'shows another position of operation of a portion of FIG. 5',

FIG. 7 shows still another position of operation of a portion of FIG. 5; 1

FIG. 8 shows a peripheral contour of a grinding wheel being dressed in accordance with the present invention; I FIG. 9 shows another peripheral contour of a grinding wheel being dressed in accordance with the present invention; and,

FIG. 10 is a partial exploded view of the apparatus shown in FIG.

I DESCRIPTION OF THE INVENTION Referring now to the drawings, and particularly to FIGS. 1 and 2 thereof, a table I is slidably mounted'on a grinding machine bed, not shown, for movement along a line parallel to the axis of a grinding wheel 3 to be dressed. A supporting bracket 2 is slidably mounted on the table 1 and is secured thereto by means of clamping bolts 4. The supporting bracket 2 has on its topend a sliding surface 5 on which a dressing housing 6 is slidably mounted. The dressing housing 6 is pivotally connected to a lower projection7 of the supporting bracket 2 by a pivot pin 8 for permitting sliding movement thereon in a horizontal plane.

A shaft 9 is slidably received for movement in a hori- 'zontal plane in the upper portion of the dressing housing 6, being restrained against rotation by a pin 10 keyed thereto, and is so arranged that the axis thereof passes through the projected axis of the pivot pin 8. The shaft 9 has a dressing tool 11 fixed thereto at one end for dressing the peripheral surface of the grinding wheel 3 to a predetermined shape, and its other end has a threaded bore in which a threaded end 12 of a shaft 13 having a knob 14 secured to the opposite end is threadably received. Rotation of the knob 14 thus causes axial movement of the shaft 9 and the dressing tool 11 in a direction determined by the direction of knob rotation. An index mark 15 on the dressing housing 6 indicates an appropriate graduation marked on a scale ring 16 which is rotatably mounted on the knob 14 and secured thereto by a clamp screw 17. A coil spring 18 is interposed between the housing 6 and the shaft 9 for eliminating backlash of the threaded engagement between the shafts 9 and 13.

As shown in greater detail in FIG. 3, a positioning member 19 is pivotally mounted on the upper side of the dressing housing 6 through a pivot pin 20 for swinging movement in a vertical plane. The positioning member 19 is provided with a reference edge 2l-for positioning the dressing tool 11. When the positioning member 19 is rotated in a counterclockwise direction, as seen in FIG. 3, from a vertical to a horizontal position into engagement with a stop member 22 secured on the dressing housing 6, the reference edge 21 is located in an operative position where it is at right angles with the axis of the shaft 9, facing the dressing tool 11 and being spaced apart from the projected axis of the pivot'pin 8 by a predetermined distance I. On the other hand, when the positioning member 19 is rotated clockwise through 90 from its operative position, the reference edge 21 is located in an inoperative position where it does not interfere with the dressing operation. A hand lever 23 is secured to the dressing housing 6 for manually rotating the same in its horizontal plane of movement, and stop members 24 and 25, shown in FIG. 1, are provided on opposite ends of the sliding surface 5 for limiting the rotation of the dressing housing 6 about the pivot pin 8 to movement through a path of 180.

The supporting bracket 2 is provided with a vertically oriented cylindrical surface 26 to which a cylindrical stop member 27 is bolted, as shown in FIG. 2, with a portion thereof projecting out from the cylindrical surface 26, in such a manner that the axis of the stop member 27 is at right angles with the axis of the grinding wheel 3 and passes through the projected axis of the pivot pin 8. An arcuate guide surface 28 is provided by a partly-circular groove in the cylindrical surface 26 and the stop member 27 being formed therein in such a manner that its center lies on the projected axis of the pivot pin 8.

The shaft 29 is slidably and rotatably received in a bore in the dressing housing 6 and is so arranged that the axes of the shafts 9 and 29 and the pivot pin 8, and the reference edge 21 are all contained in a common vertical plane. A reduced end portion 30 of the shaft 29 extends through a cap 31 secured over the bore in the dressing housing 6. A coil spring 32 interposed between the shaft 29 and the cap 31 urges the shaft 29 toward the grooved or channeled guide surface 28. The shaft 29 has a bore in its other end, the diameter of which is slightly larger than the outer diameter of the cylindrical stop member 27 so as to easily receive the projected end of the stop member 27 therein. The end of the shaft 29 adjacent the guide surface 28 has a projection 33 of semi-circular shape in cross-section, as best shown in FIG. 10. A cylindrical member 34 is slidably received in the bore of the shaft 29 and rotatably carries a circular roller 35 by means of a vertical pin 36 forming the supporting axis thereof. Seated between the cylindrical sliding member 34 and the inner end of the bore in the shaft 29 is a spring 37 for holding the roller 35 in rotatable engagement with the guide surface 28 of the dressing housing 6.

A knob 38 is secured to the end of the reduced portion 30 of the shaft 29 and has a pin 39 press-fitted thereto. The cap 31 has four dead end holes 40, 41, 42 and 43, as shown in FIG. 4, cooperatively associated with the pin 39 and being equi-angularly spaced apart from each other. The depths of the holes 41, 42 and 43 are the same and are deeper than the hole 40. The arrangement between the stop member 27, the projection 33 of the shaft 29, the hole 42 of the cap 31 and the pin 39 of the knob 38 is such that when the pin 39-is inserted into the hole 42, as shown in FIG. 5, the semicircular projection 33 is engaged with the lower portion of the stop member 27 to lock the dressing housing 6 against relative sliding movement with respect to the supporting bracket 2. I

In operation, when it is desired to dress the peripheral portion of the grinding wheel having part-circular portions 50 and 51 at the opposite sides thereof, as shown in FIG. 8, the reference edge 21 is moved into its operative position with the pin 39 being inserted into the hole 42 thereby to lock against relative sliding movement between the supporting bracket 2 and the dressing housing 6. The dressing tool 11 is then moved axially by rotating the knob 14 to be engaged with the reference edge 21. Subsequently, the dressing tool 11 is again moved axially to be positioned in a predetermined position corresponding to the radius of the partcircular portions 50 and 51 of the grinding wheel 3, while observing the value indicated by the index mark 15 on the dressing housing 6. With the dressing tool 11 being adjusted, the reference edge 21 is moved into its inoperative position. The table 1 is then moved parallel to the axis of the grinding wheel 3 by means of a suitable mechanism, not shown, to position the dressing tool 11 to a position indicated at 52, as shown in FIG. 8. Knob 38 is then moved outwardly away from the cap 31 against the spring 32 and thereafter rotated to insert the pin 39 into the hole 43. With the pin 32 being inserted into the hole 43, the dressing housing 6 is rotatable only within a limited range between the stop members 25 and 27. Therefore, when the hand lever 23 is rotated in a horizintal plane, the dressing housing 6 is rotated about the pivot pin 8 along the guide surface 28 to dress the part-circular portion 50 of the grinding wheel 3.

Upon completion of dressing the part-circular portion 50, the pin 39 is inserted into the hole 42 with the dressing tool 11 being positioned at 52 to lock against relative movement between the supporting bracket 2 and the dressing housing 6. The table 1 is then moved parallel to the axis of the grinding wheel 3 to dress the straight portion 53 of the grinding wheel 3.

Upon completion of dressing the straight portion 53, the dressing tool 11 is positioned at 54, as shown in FIG. 8, and the pin 39 is then inserted into the hole 41, as shown in FIG. 6. With the pin 39 being inserted into the hole 41, the dressing housing 6 is rotatable only within a limited range between the stop members 24 and 27. Therefore, when the hand lever 23 is rotated in a horizontal plane, the dressing housing 6 is rotated about the pivot pin 8 along the guide surface 28 to dress the part-circular portion 51 of the grinding wheel 3.

When it is desired to dress a peripheral portion 55 of the grinding wheel 3 in a circular shape, as shown in FIG. 9, the dressing tool 11 is adjusted to'a predetermined position corresponding to the radius of the peripheral portion 55 by rotating the knob 14 with the pin 39 being inserted into the hole 42 thereby to lock against relative sliding movement between the supporting bracket 2 and the dressing housing 6. The table 1 is then moved parallel to the axis of the grinding wheel 3 to position the dressing tool at the center of the width of the grinding wheel 3, as indicated at 56 in FIG. 9.

The pin 39 is thereafter inserted into the hole 40, as

shown in FIG. 7. With the pin 39 being inserted into the hole 40, the projection 33 of the shaft 29 is disengaged from the stop member 27, since the depth of the hole 40 is shallower than those of the other holes, thereby permitting the dressing housing 6 to rotate freely relative to the supporting bracket 2 within the range between the stop members 24 and 25. Therefore, when the hand lever 23 is rotated in a horizontal plane, the dressing housing 6 is rotated through -l80 about the pivot pin 8 along the guide surface 28 to dress the peripheral portion 55 of the grinding wheel 3 in a prede' termined shape.

While the invention has been'describ'ed by means of a specific embodiment, many modifications and variations are obviously possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A dressing apparatus for manually dressing a grinding wheel comprising:v

a table slidable in a path parallel to the axis of the grinding wheel;

a supporting bracket mounted on said table;

a dressing housing slidably mounted on said supporting bracket and being connected thereto by a pivot pin for permitting sliding movement about said pivotpin in a horizontal plane;

a first shaft slidably but not-rotatably received in said I dressing housing with the axis thereof passing through the axis of said pivot pin;

a dressing tool secured to said first shaft for dressing the grinding wheel;

means for adjusting-an axial position of said dressing tool;

a positioning member on said dressing housing in its operative state having a reference edge thereon lying in a vertical plane including the axis of said first shaft and being spaced apart from the axis of said pivot pin by a predetermined distance;

measuring means for measuring the position of said dressing tool relative to said reference edge;

a manual hand lever for rotating said dressing housing in a horizontal plane; and,

selective meansfor selectively permitting said dressing housing to be rotated freely within predetermined limits and to be locked against rotation relative to said supporting bracket, said selective means comprising, a cylindrical stop member mounted on said supporting bracket, a second shaft slidably and rotatably received in said dressing housing and having at one end thereof a projection inthe form of a substantiallysemi-circular shape in cross-section being cooperatively associated with stop member, means defining a bore in said second shaft having a diameter which is slightly larger than the outer diameter of said cylindrical stop member for permitting said stop member to be received therein, a resilient member for urging said second shaft toward said cylindrical stop member, and means for selectively indexing said second shaft to four angularly and equally spaced positions relative to said cylindrical stop member.

2. A dressing apparatus as set forth in claim 1, wherein said positioning member is pivotally mounted on said dressing housing, and further comprising a stop member on one of said dressing housing and said positioningmember for positioning said reference edge to an operative positionwhere said reference edge is at right angles with the axis of said first shaft and is spaced apart from the axis of said pivot pin by a predetermined distance.

3. A dressing apparatus as set forth in claim 1, wherein said cylindrical stop member is disposed with the axis thereof being at right angles with the axis of said grinding wheel and passing through the axis of said pivot pin.

4. A dressing apparatus as set forth in claim 1, wherein the axes of said first and second shafts and said pivot pin lie in a common vertical plane.

5. A dressing apparatus as set forthin claim 1, further 6. A dressing apparatus as set forth in claim 1, wherein a pair of stop members are provided on said supporting bracket for limiting rotational movement of said dressing housing within a predetermined mage.

7. A dressing apparatus for manually dressing a grinding wheel comprising:

a table slidable in a path parallel to the axis of the grinding wheel;

a supporting bracket mounted on said table;

a dressing housing slidably mounted on said support-' ing bracket and being connected thereto by a pivot pin for permitting sliding movement about said pivot pin in a horiziontal plane;

a first shaft slidably but non-rotatably received in said dressing housing with the axis thereof passing through the axis of said pivot pin;

a dressing tool secured to said first shaft for dressing the grinding wheel;

means for adjusting an axial position of said dressing tool,

a positioning member on said dressing housing in its operative state having a reference edge thereon lying in a vertical plane including the axis of said first shaft and being spaced apart from the axis of said pivot pin by a predetermined distance;

measuring means for measuring the position of said dressing tool relative to said reference edge;

a manual hand lever for rotating said dressing housing in a horizontal plane; and,

selective means for selectively permitting said dressing housing to be rotated freely within predeter mined limits and to be locked against rotation relative to said supporting bracket,

wherein said selective means comprises a cylindrical stop member mounted on said supporting bracket, a second shaft slidably and rotatably received in said dressing housing having a reduced portion at one end extending through a cap member secured to said dressing housing and having a projection at its other end in the form of a substantially semicircular shape in cross-section, means defining a bore in said second shaft having a diameter which is slightly larger than the outer diameter of said cylindrical stop member for permitting said cylindrical stop member to be received therein, a resilient member, interposed between said second shaft and said cap member for urging said second shaft toward said cylindrical stop member, a knob member mounted on said reduced end portion of said second shaft, a pin member secured to said knob member, and said cap member having four equiangularly spaced dead end holes, the arrangement between said pin member, a first hole of said four holes, the projection of said second shaft and .the cylindrical stop member being such that when pin member is inserted into said first hole, the projection is engaged with a lower portion of said cylindrical stop member for locking against relative rotation between said supporting bracket and said dressing housing, and the depth of a second hole of said four holes positioned diametrically opposite said first hole being shallower than the other three holes so that when the pin member is inserted into said second hole, the projection of said second shaft is disengaged from said stop member thereby permitting said dressing housing to be rotated freely relative to said supporting bracket.

8. A dressing apparatus as set forth in claim 7, wherein the axis of said cylindrical'stop member is at right angles with the axis of said grinding wheel and passes through the axis of said pivot pin.

9. A dressing apparatus as set forth in claim 7, wherein the axes of said first and second shafts and said pivot pin lie in a common vertical plane.

10. A dressing apparatus as set forth in claim 7, further comprising:

an arcuate guiding channel formed on said supporting bracket and said stop member with the center thereof being positioned at the center of said pivot a sliding member slidably received in said means defining a bore in said second shaft; a roller rotatably carried on said sliding member;

and, I

a resiient member interposed between said second shaft and said sliding member for urging said roller into rotatable engagement with said guiding channel.

11. A dressing apparatus as set forth in claim 7, wherein a pair of stop members are provided on said supporting bracket for limiting rotational movement of said dressing housing within a predetermined range. 

1. A dressing apparatus for manually dressing a grinding wheel comprising: a table slidable in a path parallel to the axis of the grinding wheel; a supporting bracket mounted on said table; a dressing housing slidably mounted on said supporting bracket and being connected thereto by a pivot pin for permitting sliding movement about said pivot pin in a horizontal plane; a first shaft slidably but not-rotatably received in said dressing housing with the axis thereof passing through the axis of said pivot pin; a dressing tool secured to said first shaft for dressing the grinding wheel; means for adjusting an axial position of said dressing tool; a positioning member on said dressing housing in its operative state having a reference edge thereon lying in a vertical plane including the axis of said first shaft and being spaced apart from the axis of said pivot pin by a predetermined distance; measuring means for measuring the position of said dressing tool relative to said reference edge; a manual hand lever for rotating said dressing housing in a horizontal plane; and, selective means for selectively permitting said dressing housing to be rotated freely within predetermined limits and to be locked against rotation relative to said supporting bracket, said selective means comprising, a cylindrical stop member mounted on said supporting bracket, a second shaft slidably and rotatably received in said dressing housing and having at one end thereof a projection in the form of a substantially semicircular shape in cross-section being cooperatively associated with stop member, means defining a bore in said second shaft having a diameter which is slightly larger than the outer diameter of said cylindrical stop member for permitting said stop member to be received therein, a resilient member for urging said second shaft toward said cylindrical stop member, and means for selectively indexing said second shaft to four angularly and equally spaced positions relative to said cylindrical stop member.
 2. A dressing apparatus as set forth in claim 1, wherein said positioning member is pivotally mounted on said dressing housing, and further comprising a stop member on one of said dressing housing and said positioning member for positioning said reference edge to an operative position where said reference edge is at right angles with the axis of said first shaft and is spaced apart from the axis of said pivot pin by a predetermined distance.
 3. A dressing apparatus as set forth in claim 1, wherein said cylindrical stop member is disposed with the axis thereof being at right angles with the axis of said grinding wheel and passing through the axis of said pivot pin.
 4. A dressing apparatus as set forth in claim 1, wherein the axes of said first and second shafts and said pivot pin lie in a common vertical plane.
 5. A dressing apparatus as set forth in claim 1, further comprising: an arcuate guiding channel formed in sad supporting bracket And said cylindrical stop member, the center thereof being positioned at the center of said pivot pin; a sliding member slidably received in said means defining a bore in said second shaft; a roller rotatably carried on said sliding member; and, a resilient member interposed between said second shaft and said sliding member for urging said roller into rotatable engagement with said guide channel.
 6. A dressing apparatus as set forth in claim 1, wherein a pair of stop members are provided on said supporting bracket for limiting rotational movement of said dressing housing within a predetermined rnage.
 7. A dressing apparatus for manually dressing a grinding wheel comprising: a table slidable in a path parallel to the axis of the grinding wheel; a supporting bracket mounted on said table; a dressing housing slidably mounted on said supporting bracket and being connected thereto by a pivot pin for permitting sliding movement about said pivot pin in a horiziontal plane; a first shaft slidably but non-rotatably received in said dressing housing with the axis thereof passing through the axis of said pivot pin; a dressing tool secured to said first shaft for dressing the grinding wheel; means for adjusting an axial position of said dressing tool; a positioning member on said dressing housing in its operative state having a reference edge thereon lying in a vertical plane including the axis of said first shaft and being spaced apart from the axis of said pivot pin by a predetermined distance; measuring means for measuring the position of said dressing tool relative to said reference edge; a manual hand lever for rotating said dressing housing in a horizontal plane; and, selective means for selectively permitting said dressing housing to be rotated freely within predetermined limits and to be locked against rotation relative to said supporting bracket, wherein said selective means comprises a cylindrical stop member mounted on said supporting bracket, a second shaft slidably and rotatably received in said dressing housing having a reduced portion at one end extending through a cap member secured to said dressing housing and having a projection at its other end in the form of a substantially semi-circular shape in cross-section, means defining a bore in said second shaft having a diameter which is slightly larger than the outer diameter of said cylindrical stop member for permitting said cylindrical stop member to be received therein, a resilient member, interposed between said second shaft and said cap member for urging said second shaft toward said cylindrical stop member, a knob member mounted on said reduced end portion of said second shaft, a pin member secured to said knob member, and said cap member having four equiangularly spaced dead end holes, the arrangement between said pin member, a first hole of said four holes, the projection of said second shaft and the cylindrical stop member being such that when pin member is inserted into said first hole, the projection is engaged with a lower portion of said cylindrical stop member for locking against relative rotation between said supporting bracket and said dressing housing, and the depth of a second hole of said four holes positioned diametrically opposite said first hole being shallower than the other three holes so that when the pin member is inserted into said second hole, the projection of said second shaft is disengaged from said stop member thereby permitting said dressing housing to be rotated freely relative to said supporting bracket.
 8. A dressing apparatus as set forth in claim 7, wherein the axis of said cylindrical stop member is at right angles with the axis of said grinding wheel and passes through the axis of said pivot pin.
 9. A dressing apparatus as set forth in claim 7, wherein the axes of said first and second shafts and said pivot pin lie in a common vertical plane.
 10. A dressing apparatus as set forth in claim 7, further Comprising: an arcuate guiding channel formed on said supporting bracket and said stop member with the center thereof being positioned at the center of said pivot pin; a sliding member slidably received in said means defining a bore in said second shaft; a roller rotatably carried on said sliding member; and, a resiient member interposed between said second shaft and said sliding member for urging said roller into rotatable engagement with said guiding channel.
 11. A dressing apparatus as set forth in claim 7, wherein a pair of stop members are provided on said supporting bracket for limiting rotational movement of said dressing housing within a predetermined range. 